Secondary oil recovery process using oxyalkylated additives

ABSTRACT

A process for the recovery of hydrocarbon materials from a subterranean hydrocarbon-bearing formation by contacting the formation with an aqueous alkaline flooding medium containing a solubilizing agent. Useful solubilizing agents include for example, block-type compounds of the formula: ##STR1## wherein n is an integer of from 1 to about 10 and m is an integer of about 5 to about 40.

This application is a continuation-in-part of application Ser. No.451,712, filed Mar. 15, 1974, now abandoned.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to an improved process for the recovery ofhydrocarbon materials from hydrocarbon-bearing formations. Moreparticularly, the invention relates to a process in which hydrocarbons,including asphaltic crudes, are recovered from a reservoir by contactingthe formation with an aqueous alkaline flooding medium containing asolubilizing agent.

2. Description of the Prior Art

The production of petroleum products is usually accomplished by drillinginto a hydrocarbon-bearing formation and utilizing one of the well-knownrecovery methods for the recovery of the hydrocarbons. However, it isrecognized that these primary recovery techniques may recover only aminor portion of the petroleum products present in the formationparticularly when applied to reservoirs of viscous crudes. Even the useof improved recovery practices involving heating, miscible flooding,water flooding and steam processing may still leave up to 70-80% of theoriginal hydrocarbons in place.

Thus, many large reserves of petroleum fluids from which only smallrecoveries have been realized by present commercial recovery methods,are yet to reach a potential recovery approaching their estimatedoil-in-place.

Water flooding is one of the more widely practiced secondary recoverymethods. A successful water flood may result in recovery of 30-50% ofthe original hydrocarbons left in place. However, generally theapplication of water flooding to many crudes results in much lowerrecoveries.

The newer development in recovery methods for heavy crudes is the use ofsteam injection which has been applied in several modifications,including the "push-pull" technique and through-put methods, and hasresulted in significant recoveries in some areas. Crude recovery by thisprocess is enhanced through the beneficial effects of the drasticviscosity reduction that accompanies an increase in temperature. Thisreduction in viscosity facilitates the production of hydrocarbons sinceit improves their mobility, i.e., it increases their ability to flow.

However, the application of these secondary recovery techniques todepleted formations may leave major quantities of oil-in-place, sincethe crude is tightly bound to the sand particles of the formation, thatis, the sorptive capacity of the sand for the crude is great. Inaddition, interfacial tension between the immiscible phases results inentrapping crude in the pores, thereby reducing recovery. Anotherdisadvantage is the tendency of the aqueous drive fluid to finger, sinceits viscosity is considerably less than that of the crude, therebyreducing the efficiency of the processes.

Consequently, process modifications have been developed which mayincorporate additives to lessen the above cited disadvantages andthereby improve the efficiency of these processes. For example,surface-active agents and miscible liquids are utilized to decrease theinterfacial tension between the water and the reservoir crude, andthickeners have been developed to adjust viscosity so as to inhibitfingering.

The practiced methods for the injection of additives commonly consist ofinjection of a slug of additive, contained in a transporting medium,e.g. water, into the formation and then following this injection with aflood water to move the additive slug through the formation. In itsideal effect, the so-called slug moves through the formation as anadditive bank, thereby imparting its beneficiating effects to therecovery process.

In many hydrocarbon-bearing formations it is common to find the oilsands to be preferentially wetted by oil. It is well known in the art toinject into these preferentially oil-wetted formations certain chemicalsto reverse the wettability characteristics of the formation, therebyincreasing the effectiveness of a water flood to remove the residualcrude. For example, a dilute alkaline aqueous solution is known toincrease the wetting characteristics of sand surfaces, and promote aleaching action and emulsification of the tarry materials. Thosesolutions have been used as slugs in conjunction with subsequent steaminjection processes to force the emulsions thus formed through theformation to a production well.

Improved recoveries from heavy crudes or tar sands have been realizedalso by the use of dilute aqueous alkaline solutions containing aneffective amount of non-ionic surfactant, whereby extraction is effectedby the spontaneous emulsification when the aqueous liquid comes incontact with the tar in the sand.

However, some of the disadvantages of those additive recovery processesinclude the problem that the additive may be strongly absorbed in thesurfaces of the sand formation, resulting in a large or excessive amountof additive being required. The costs involved of these additives, whichmay be relatively expensive, may become excessive early in the life ofthe recovery process necessitating its termination. Other disadvantagesinclude the unfavorable viscosity ratio between the flooding medium andthe crude.

It is known that the recovery of oil by injection of water or otherfluids varies substantially from one formation to another and it isbelieved that the asphalt content of the hydrocarbons of some formationsis at least a major factor responsible for this variation. A variety ofknown asphalt dispersants have been employed in flooding media on thetheory that such materials would substantially improve hydrocarbonrecovery in those instances where asphalt was present in the nativehydrocarbon, however, the use of such materials has not beenparticularly effective, probably because of the limited solubility ofsuch agents in the normally employed flooding fluids. There is adefinite need in the art, therefore, for a recovery process employingasphalt dispersants with improved solubility characteristics.

One of the principal objects of this invention is to provide an improvedprocess for increasing the ultimate recovery of hydrocarbon from ahydrocarbon-bearing formation.

Another object of this invention is to provide an efficient method forthe recovery of hydrocarbon from a hydrocarbon-bearing formation inwhich an aqueous alkaline flooding medium containing as a solubilizingagent a watersoluble, oxyalkylated, nitrogen-containing aromaticcompound is utilized.

BRIEF SUMMARY OF THE INVENTION

This invention relates to a method for recovering hydrocarbons from asubterranean hydrocarbon-bearing formation having in communicationtherewith at least one injection well and one production wellcomprising:

(a) injecting into the said formation through said injection well anaqueous alkaline flooding medium containing a solubilizing agentcomprising a solution of a nitrophenol which has been first reacted withpropylene oxide and then with ethylene oxide or of a nitrophenol whichhas first been reacted with a mixture of ethylene oxide and propyleneoxide and then with ethylene oxide, made alkaline with sodium hydroxide,

(b) forcing said alkaline flooding medium through the formation, and

(c) recovering hydrocarbons through said production well.

DETAILED DESCRIPTION OF THE INVENTION

The aqueous alkaline flooding medium employed in the process of thisinvention comprises an aqueous medium which can be, for example, steam,hot water, a mixture of hot water and steam or cold water together withan alkaline agent containing a solubilizing agent or a mixture ofsolubilizing agents. Useful alkaline agents includes compounds selectedfrom the group consisting of an alkali metal hydroxide, alkali metalhypochlorites, an alkaline earth metal hydroxide and a basic salt of thealkali metal or alkaline earth metal which is capable of hydrolyzing inan aqueous medium to given an alkaline solution, the concentration ofthe alkaline agent being about 0.001 to about 0.5 molar to give therequired alkaline solution. Examples of the especially useful alkalineagents include sodium hydroxide, potassium hydroxide, lithium hydroxide,ammonium hydroxide, sodium hypochlorite, potassium hypochlorite, sodiumcarbonate and potassium carbonate, etc.

solubilizing materials useful in the process of this invention includewater-soluble, oxyalkylated nitrogencontaining aromatic compounds wherepreferably the aromatic compound contains not more than 12 carbon atomsand the number of oxyalkyl units is about 5 to about 50.

An especially useful group of the water-soluble, oxyalkylated,nitrogen-containing aromatic compounds include compounds of the formula:

    R(OR').sub.m OH

wherein R is selected from the group consisting of: ##STR2## wherein R'is alkylene of from 2 to 4 inclusive carbon atoms, and m is an integerof from about 5 to about 50 and preferably, from about 5 to about 20.

The above-listed water-soluble oxyalkylated products of this inventioncan be conveniently prepared by a number of processes well-known in theart. For example, the alkylene oxide or mixture of alkylene oxides canbe reacted with the initiator dissolved in a suitable solvent throughoutwhich an alkaline catalyst, such as potassium hydroxide or sodiumhydroxide, in uniformly dispersed. The quantity of the catalyst utilizedgenerally will be from about 0.15 to about 1.0 percent by weight of thereactants. Preferably, the reaction temperature will range from about80° C to about 180° C while the reaction time will be from about 1 toabout 20 hours or more depending on the particular reaction conditionsemployed. This process is more completely described in U.S. Pat. No.2,425,845.

Another especially suitable group of solubilizing compounds useful inthe process of this invention include oxyalkylated derivativescontaining block polypropylene and polyethylene groups having theformula: ##STR3## wherein n is an integer of from 1 to about 10 and m isan integer of from 5 to about 40 and, preferably, n is an integer offrom 4 to about 8 and m is an integer of from 5 to about 20.

Compounds of the above formula can be prepared by well-known methodssuch as taught, for example, in U.S. Pat. Nos. 3,062,747; 2,174,761 orin 2,425,755. In general, the procedure consists in condensing anitrophenol with propylene oxide in the presence of an oxyalkylationcatalyst until the required amount of the oxide has reacted thencontinuing the oxyalkylation reaction with the ethylene oxide until thedesired block oxyalkylated polymer is formed.

Heteric oxyalkylated nitrophenols are also useful as solubilizing agentsin the process of this invention such as for example, heteric (i.e.,random) copolymers of ethylene oxide and propylene oxide prepared byreacting a mixture of ethylene oxide and propylene oxide with anitrophenol and then reacting the thus-formed heteric product withethylene oxide to form compounds of the formula: ##STR4## wherein thesum of r plus s is an integer of from 2 to about 12 and with the provisothat r and s are each not less than 1, t is an integer of from 5 toabout 32 and preferably r is an integer of from 2 to about 6, s is aninteger from 3 to about 6 and t is an integer of from 5 to about 20.Compounds of this type can be prepared by a variety of methods wellknown in the art such as by the processes set forth in U.S. Pat. No.2,425,755 and 2,425,845.

The solubilizing agent should be present in the aqueous solution insufficient concentration to effect the emulsification of the hydrocarbonmaterial and maintain them in this state during passage through theformation. Concentrations in solutions of from about 0.05 to about 5.0percent by weight of the solubilizing agent are usually sufficient,although smaller or larger amounts may be employed satisfactorily insome cases.

The advantageous results achieved with the aqueous alkaline floodingmedium used in the process of this invention are believed to be derivedfrom the wettability improving characteristics of the alkaline agent andthe solubilizing action of the solubilizing agent on the crude oil suchas in tar sands and in other formations and especially on the asphaltenefractions. The solubilizing agent is believed to be effective inreleasing the crude from the pore surfaces or the sand surfaces as thecase may be so that the surfaces can be exposed to the alkaline agent.

A further advantage of the aqueous alkaline flooding medium of thisinvention is believed to result from its ability to emulsify theextracted crude to form an oil in water emulsion. The effectiveness ofthe flooding medium is also thought to result to a great extent from itsaction on the heavier complex hydrocarbon materials referred to asasphaltenes present to some extent in all crudes and especially inlow-gravity viscous crudes and oils such as those found in tar sandswhich are extremely difficult to recover. It has been shown thatasphaltene fractions are reresponsible in a large part for the adhesiveforce which many oils and especially heavy crudes and tars have for themineral surfaces of the hydrocarbon-bearing formations.

In operating the process of this invention one embodiment may consist ofdrilling an injection well into the formation through which the aqueousflooding medium is injected into the formation. The flooding medium maybe injected continuously or a slug of the aqueous alkaline floodingmedium containing the solubilizing agent may be injected into theformation followed by injection of a slug of an aqueous drive fluid suchas water, hot water, or steam.

During the passage of the aqueous alkaline flooding medium of thisinvention which contains the solubilizing agent hydrocarbons arestripped from the formation, forming an oil-in-water emulsion which canthen be produced at neighboring wells. Recovery of the hydrocarbons fromthe emulsion can be accomplished by any one of several well knownemulsion breaking techniques.

PREPARATION OF ETHOXYLATED-8-HYDROXY QUINOLINES

A series of four polyethoxylated-8 hydroxy quinoline solubilizing agentshaving the general formula: ##STR5## where n is the number of oxyethylunits were prepared as described below:

To a 250 ml reaction flask there was added 27.2 grams (0.068 mole) ofpolyethylene glyol (mol. wt. 400) and 3.7 grams (0.066 mole) ofpotassium hydroxide. The reaction mixture was heated gently until thepotassium hydroxide had dissolved at which time the temperature of thecontents of the flask was about 80° C. A total of 9.7 grams (0.0625mole) of 8-hydroxyquinoline was added to the reaction flask over aperiod of 10 minutes after which the reaction mixture was heated to135°-140° C. and held at that temperature for 4 hours. After standingovernight, the reaction mixture was steam distilled to remove unreactedpolyethylene glycol and water was then removed from the oxyalkylatedproduct by evaporation. Yield: 33 grams. The molecular weight of theproduct was determined in dimethyl formamide solution using a vaporpressure osmometer and found to be 478 (Product B).

Three additional polyethoxylated products were prepared (i.e., ProductsA, C and D) utilizing 8-hydroxyquinoline as the initiator in the samemanner as described above except that polyethylene glycols havingrespectively molecular weights of 300, 600 and 1000 were employed.Details relating to these four polyethoxylated compounds are set forthin Table 1 which follows:

                  TABLE 1                                                         ______________________________________                                        MOLECULAR WEIGHTS OF POLYETHOXYLATED-8-                                       HYDROXYQUINOLINES                                                             PRODUCT   MOLECULAR WEIGHT   n                                                ______________________________________                                        A         365                5                                                B         478                8                                                C         630                11                                               D         886                17                                               ______________________________________                                        PREPARATION OF ETHOXYLATED 8-QUINOLINE                                        SULFONIC ACID                                                                 ______________________________________                                    

Equal quantities by weight of 8-quinolinesulfonic acid and phosphorouspentachloride were ground together in a mortar. This mixture was thenrefluxed at approximately 140° C. for 3 hours after which work-up of thereaction mixture gave 8-quinolinesulfonyl chloride.

Seven grams (0.031 moles) of the 8-quinolinesulfonyl chloride wasgradually added to a mixture of polyethylene glycol (mol. wt. 600, 0.034moles) and 1.7 grams of potassium hydroxide which had been pre-heated to95° C. The mixture was then heated to a temperature of 140°-150° C. andallowed to remain at that temperature for 4 hours. After work-up theproduct, ethoxylated 8-quinolinesulfonic acid, was obtained in about 75percent yield. The molecular weight of the product was determined at 62°C. in dimethyl formamide solution utilizing a vapor pressure osmometerand found to be 764 (theoretical 791).

Three additional ethoxylated quinoline sulfonic acid derivatives wereprepared in the same manner as described above by reacting equimolarquantities of polyethylene glycol having a molecular weight of 200, 400and 1000 respectively with 8-quinolinesulfony chloride. In each instancethe yield of the desired product was about 75 percent.

PREPARATION OF BLOCK POLYPROPYLENE, POLYETHYLENE REACTION PRODUCTS WITHNITROPHENOL

One mole of p-nitrophenol is by stabilization to an autoclave and 0.1weight percent of powdered potassium hydroxide catalyst based on theweight of the phenol is added following which the autoclave is sealed,flushed with nitrogen, and heated to 150° C. Next three moles ofpropylene oxide are gradually fed in and after about three hours withstirring the reaction is complete as indicated bystabilization ofpressure. A total of six moles of ethylene oxide is then introduced intothe autoclave maintained at 150° C and after about three hours theaction is complete. The block-type reaction product, an amber-colored,oily, viscous liquid of the formula: ##STR6## is recovered insubstantially quantitative yield. If desired, the catalyst can beremoved from the product by neutralization with an acid such asphosphoric acid, followed by filtration.

PREPARATION OF REACTION PRODUCTS OF NITROPHENOL WITH A MIXTURE OFETHYLENE OXIDE AND PROPYLENE OXIDE FURTHER REACTED WITH ETHYLENE OXIDE

One mole of m-nitrophenol is charged to an autoclave and 0.1 weightpercent of powdered potassium hydroxide based on the weight of thephenol is added following which the autoclave is sealed and flushed withnitrogen. Stirring is commenced and the autoclave is heated to about150° C. Then a mixture comprising 3 moles of propylene oxide and twomoles of ethylene oxide is introduced into the autoclave with stirringover a period of about 3 hours at which time the reaction is complete asevidenced by no further change in pressure. Next eight moles of ethyleneoxide are added at 150° C with stirring and after three hours there isno further change in pressure is observed indicating completion of thereaction. The catalyst is neutralized with a fatty acid and the productrecovered by filtration. The product, a viscous amber-colored liquid ofthe formula: ##STR7## is recovered in substantially quantitative yieldafter neutralization of the catalyst followed by filtration.

The following examples which illustrate various embodiments of theprocess of this invention are to be considered not limitative.

EXAMPLES I-IV

A series of flow tests utilizing as a flooding medium an aqueousalkaline flooding medium and as a solubilizing agent Products E and F iscarried out. Small sand packs are prepared using 150/200 mesh Ottawasand and having pore volumes of approximately 30 ml. The packs aresaturated with brine which is displaced with Slocum crude oil (APIgravity 17.5) to irreducible water saturation. In the next step the oilsaturation of the pack is reduced to approximately 80 percent byflooding with 8 pore volumes of distilled water. Ths initial waterfloodis followed by the injection into each pack of 8.5 pore volumes of 0.5volume percent of a solution of Products E and F respectively at threedifferent pH values, namely 7, 12 and 13. A substantial increase in theamount of oil recovered is achieved over the amount of oil recovered inseparate comparative tests with quinoline as a solubilizing agent orwith alkaline water alone.

In a like manner a substantially increased oil recovery is achievedwhen, for example, the other abovedescribed oxyalkylated products wereemployed in the process of this invention. Mixtures of Products E and Fwith any of the other oxyalkylated products previously described mayalso be employed in the recovery process of this invention.

What is claimed is:
 1. A method of recovering hydrocarbons from asubterranean hydrocarbon-bearing formation having in communicationtherewith at least one injection well and at least one production wellcomprising:a. injecting into the said formation through said injectionwell an aqueous alkaline flooding medium containing a solubilizing agentcomprising a water-soluble, oxyalkylated, nitrogen-containing aromaticcompound, b. forcing said alkaline flooding medium through the formationand, c. recovering hydrocarbons through said production well, whereinthe said water-soluble oxyalkylated, nitrogencontaining aromaticcompound is selected from the group consisting of: A. a block-type,water-soluble, oxyalkylated compound of the formula: ##STR8## wherein nis an integer of from 1 to about 10 and m is an integer of from 5 toabout 40, and B. a random-type, water-soluble oxyalkylated compoundwhich has been further reacted with ethylene oxide having the formula:##STR9## wherein the sum of r plus s is an integer of from 2 to about 12and with the proviso that r and s are each not less than 1 and t is aninteger of from 5 to about 32 and wherein the said aqueous alkalineflooding medium contains an alkaline agent selected from the groupconsisting of alkali metal hydroxides, alkali metal hypochlorites,alkaline earth metal hydroxides, and mixtures thereof.
 2. The method ofclaim 1 wherein the said nitrogen-containing compound has the formula:##STR10## wherein n is an integer of from 1 to about 10 and m is aninteger of from 5 to about
 40. 3. The method of claim 1 wherein the saidnitrogen-containing aromatic compound is a random type oxyalkylatedcompound which has been further reacted with ethylene oxide and has theformula: ##STR11## wherein the sum of r plus s is an integer of from 2to about 12, and with the proviso that r and s are each not less than 1and t is an integer of from 5 to about
 32. 4. The method of claim 1wherein the said nitrogen-containing aromatic compound is: ##STR12## 5.The method of claim 1 wherein the said nitrogen-containing aromaticcompound is prepared by oxyalkylating m-nitrophenol with a mixture ofthree moles of propylene oxide and two moles of ethylene oxide and thenwith eight moles of ethylene oxide and has the formula: ##STR13##
 6. Themethod of claim 1 wherein the said aqueous alkaline flooding mediumcomprises an aqueous medium containing an alkaline agent selected fromthe group consisting of alkali metal hydroxides, alkali metalhypochlorites, alkaline earth metal hydroxides and mixtures thereof. 7.The method of claim 6 wherein said alkaline agent is sodium hydroxide.8. The method of claim 6 wherein the said alkaline agent is contained inthe aqueous medium in amounts in the range of from about 0.001 to about0.5 molar.
 9. The method of claim 6 wherein the said aqueous medium issteam.